This invention relates generally to photosensitive devices useful, for example, in digital cameras, scanners, imaging sensors and the like.
Complementary Metal Oxide Semiconductor (CMOS) image sensors are an attractive alternative to conventional charge coupled device (CCD) image sensors. This is in part due to the possibility of lower power consumption, integration of on-chip computation and lower cost associated with the CMOS image sensors. Conventional CMOS image sensors detect light in the visible spectrum. These a devices are commonly used as the image sensors in digital cameras, scanners and similar devices. An infrared filter, associated with a CMOS image sensor, removes the infrared component from ambient light. Thus, the image sensor is only exposed to light in the visible spectrum.
The detection of infrared radiation has many useful applications. For example, cameras with infrared night vision could be used in security and baby monitoring applications. In addition, the infrared light patterns are useful as markers in three dimensional (3D) imaging applications. Thus, while conventional CMOS image sensors detect visible light, there are many uses for infrared light detectors.
Conventionally, photosensitive devices are sensitive to both visible light and to infrared radiation, but through the use of filters, specific wavelengths are detected. Thus, different detectors. are used to detect different wavelength spectra such as visible and infrared radiation.
However, it would be very desirable to have a single apparatus that is capable of detecting both visible and infrared spectra without substantially increasing the cost or the size of the detector.
In accordance with one aspect, a photosensitive element includes a first device which is sensitive to light in the visible spectrum. A second device is arranged beneath the first device. The second device is sensitive to light in the infrared spectrum.